1. Field of the Invention
The present invention relates to a projection display apparatus, and particularly to a projection display apparatus that uses a reflective light valve.
2. Related Background Art
Japanese Patent Application Laid-Open No. 10-133301, which is owned by the assignee of the present application, discloses a projection display apparatus in which light from a light source is color-separated into an R (red) light, a G (green) light and a B (blue) light, the color lights are then made incident on corresponding polarizing beam splitters disposed at predetermined positions respectively so as to be split, one of the polarized light components of each color light that has been emitted from the polarizing beam splitter is then made incident on a corresponding reflective light valve disposed for each color and reflected by it while modulated by a color signal of the corresponding color, the lights of the respective colors emergent from the respective reflective light valves are then analyzed by the polarizing beam splitters so that the modulated light components are picked up, and the analyzed lights of the respective colors are color-composed and thereafter projected by a projection lens.
In connection with the above-described type of projection display apparatus, it has been known to dispose a quarter-wave plates in the spaces between the light valves for the respective color lights and the polarizing beam splitters in order to enhance contrast of projected images.
The above-described projection display apparatus suffers from a problem that an image of dust adhering to the light valves is projected onto a screen by the projection lens. In addition, since the quarter-wave plate provided for the respective color lights are located at positions closed to the light valves, an image of dust adhering to the quarter-wave plate is also projected onto the screen.